The common inks for writing tools such as ball-point pens are aqueous inks and oil-based inks, and in recent years there have been proposed W/O-type emulsion inks, having an aqueous component dispersed in an oil component. Oil-based inks generally tend to have heavier writing performance. With aqueous inks, on the other hand, writing lines tend to dry more slowly and cause smearing of sheet surfaces. In contrast, W/O-type emulsion inks are noted as inks that exhibit both satisfactory writing performance and writing line drying properties.
In Patent document 1, for example, there is proposed a W/O-type emulsion ink composition that has aqueous components including water, a polyhydric alcohol, a thixotropic agent and a pigment, dispersed in an oil component that includes a polar solvent and a stringiness-imparting agent. However, aqueous ink compositions have conventionally been used as fluorescent inks for writing tools, while emulsion ink compositions are not so commonly used at the current time.